The Canon 5D is an exceptionally good camera. I bought one as my walk-around camera, and was surprised to see that my landscapes with this camera are indistiguishable from those taken with my 1DsMkII, which is the finest 35mm digital camera.
Canon lenses from 85mm and up are very sharp and produce brilliant landscapes.
For 50mm and wider you will want to buy Contax or Zeiss manual lenses (the Contax are superb and very inexpensive) and attach them to the Canon with an adapter.
Or, you can purchase the Canon 17-40 f4 and the Canon 70-200 f4, both of which are exceptionally sharp. You only need to get a 50mm to fill the gap between the two lens.
Just as important as the camera is a good tripod. I recommend the Gitzo with an Acratech head.
It is also good to get an L-bracket so that you can quickly change from landscape to portrait mode, which is very useful for stitched panoramics. A bubble level will help you to level the camera, and a remote release with mirror lock up will produce the sharpest landscapes.